Carburetors for internal combustion engines

ABSTRACT

A carburetor has a main fuel jetting system which opens in the intake pipe upstream of the throttle and an auxiliary device for cold start which comprises a conduit for delivering a fuel mixture of predetermined richness to the intake pipe. A valve actuated responsive to the temperature of the engine coolant or lubricant moves from a position for which the conduit is open to a position where it closes the conduit when the engine reaches its normal operating temperature. In addition, a choke valve located upstream of the main fuel jetting system is controlled by a temperature responsive member which maintains it in a minimum opening position when the engine is cold and opens it shortly after start.

United States Patent Schmid Apr. 15, 1975.

[ CARBURETORS FOR INTERNAL 3,361,416 1/1968 Morgan et a1. 261/39 13 COMS ENGINES 3,670,709 6/1972 Eckert 261/39 D 3,706,444 12/1972Masak1etal..... 123/119 F Inventor: Werner schmld, Esslmgen, 3,763,83710/1973 Orlando 123/119 F Germany [73] Assignee: Societe Industrielle deBrevest et Primary Exami'fer wenden Bums dEtudes S.I.B.E.,Neuilly-sur-Seine, 48mm"! Exammer-D Reymlds France Attorney, Agent, orFzrmStevens, Davis, Miller &

Mosher [22] Filed: Jan. 8, 1974 [21] Appl. No.: 431,781 [57] ABSTRACT Acarburetor has a main fuel jetting system which [30] Foreign ApplicationPriority Data opens in the intake pipe upstream of the throttle and J H1973 France 73 00950 an auxiliary dev1ce for cold start whlch compnses aconduit for delivering a fuel mixture of predetermined [52] U S Cl"3/119 23/1 19 123/l79 richness to the intake pipe. A valve actuatedrespon- 261/39 261/39 sive to the temperature of the engine coolant orlubril t C] 1 "10 cant moves from a position for which the conduit is[58] i F T open to a position where it closes the conduit when le 0 earc"56 D 39 the engine reaches its normal operating temperature. Inaddition, a choke valve located upstream of the main fuel jetting systemis controlled by a temperature [56] References cued responsive memberwhich maintains it in a minimum UNITED STATES PATENTS opening positionwhen the engine is cold and opens it 2,981,245 4/1961 Sarto 123/119 Fshortly after start, 3,198,185 8/1965 Wastas 123/119 F 3,246,886 4/1966Goodyear et al 123/119 F 4 Clams, 2 Drawmg Figures PATENTEUAPR] 519. 5

SHEET 1 0f 2 CARBURETORS FOR INTERNAL COMBUSTION ENGINES BACKGROUND OFTHE INVENTION The invention relates to carburettors for internalcombustion engines comprising. in addition to a main fuel jetting systemfor the normal operation of the engine. which opens into the intake pipeupstream of a main throttle member actuated by the operator. anauxiliary starting device for cold starting. The auxiliary startingdevice is adapted to deliver a flow-rate of fuel (and possibly aflow-rate of air) into the intake pipe in addition to the flow-ratenecessary for hot idling of the engine. and is directly or indirectlyresponsive to the temperature of the engine.

A starting device is known which consists of a starting or choke valvelocated in the intake pipe upstream of the main fuel jetting system. Thechoke valve is rotatable about an eccentric axle so that it opens underthe effect of the air flow which passes into said pipe. against theaction of a return spring. and it increases the underpressure prevailingat the mouth of the main jetting system and. consequently, the richnessof the air/fuel mixture admitted to the engine as long as the latter hasnot reached a minimum temperature.

Now regulations exist which are intended to limit atmospheric pollutionand impose that the flow-rates of air and fuel in the carburettor bemore and more accurately metered, especially when starting a warmengine. that is to say an engine whose temperature is at least equal toabout C but substantially less than the normal operating temperature ofthe engine. In order that a warm engine may be started and rotate at lowspeed. the richness of the air/fuel mixture which it receives must beslightly increased with respect to the richness corresponding to thenormal running temperature of the engine. that is when the engine ishot. it is difficult to determine this slight enrichment by means of thestarting valve since a slight error in the angular position of thisvalve involves a large modification of the richness of the slow speedmixture. and this all the more as the flow-rate of air at slow speed(idling) is smaller.

Another type of starting device is known which consists of a distributoradapted. as long as the engine has not reached its normal operatingtemperature. to open a passage which receives a mixture of air and offuel in well determined proportions and which opens into the zone of theintake pipe of the carburettor situated downstream of its principalthrottle member. However the enrichment of the mixture determined by astarting device of the second type diminishes when the load on theengine increases and in particular it is difficult to obtain asufficiently rich mixture for full load operation of an engine at verylow temperature.

It is an object of the invention to provide a carburettor which deliversa mixture whose richness is well adapted to the temperature oftheengine. whatever the condition of the latter from start.

SUMMARY OF THE INVENTION The carburettor has a starting device whichcomprises closure valve means adapted, as long as the engine has notreached its normal operating temperature. to open a passage whichreceives a mixture of air and of fuel in predetermined proportions andwhich opens into the zone of the intake pipe situated downstream of itsprincipal throttle member and a starting valve situated in the intakepipe upstream of the principal jetting system. the starting valve beingheld sufficiently open. when the engine is warm. not to substantiallyenrich the air/fuel mixture on slow' speed running and at very smallengine loads. The starting or choke valve is controlled by a firstelement sensitive to temperature which is arranged to be rapidly heatedup and the closure valve means is controlled by a second elementsensitive to temperature which is arranged to be heated up slowly. sothat the choke valve is put out of action before the closure valve meansas the engine heats up.

In this way. when the engine is cold. the enrichment is determined bothby the closure valve means and by the starting valve. When the engine iswarm. the enrichment is determined essentially by the aforesaid valvemeans. Finally. when the engine is hot. both starting devices no longeract on the richness of the mixture. The choke valve is caused to opencompletely soon after the starting of the engine and the enrichment ofthe mixture which is necessary on cold operation then is due to theaction of the closure valve.

The first element may be exposed to the temperature of an electricalresistance which is supplied from a voltage source on starting of theengine and the second element is exposed to the temperature of thelubricant or cooling fluid of the engine.

SHORT DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood from the de scription which follows of a particularembodiment. The description refers to the accompanying drawings,wherein:

FIGS. 1 and 2 show, in diagrammatic elevation with portions cut away. acarburettor constructed according to an embodiment of the invention, inwhich the posi tions of the elements correspond respectively to coldoperation and to normal operation of the engine.

DESCRIPTION OF A PREFERRED EMBODIMENT The carburettor comprises anintake pipe 1 in which is arranged. upstream of a principal throttlemember (or butterfly valve) 2 actuated by the driver. an eccentricstarting valve 3 tending to open under the effect of the air flow in thepipe 1 against a return force transmitted through a link rod 4 to alever 5, secured to the axle 6 ofthe valve 3. That construction issimilar to that described in patent application Ser. No. 346.477assigned to the assignee of the present invention and the contentthereof is included in this application by way of reference.

A fuel jetting device 67 opens in the pipe 1 at the level of a venturi68, downstream of the valve 3. The air intake 69 of the pipe I isconnected to the portion of the pipe I situated downstream of thebutterfly valve 2, in addition to the direct path. by a circuitcomprising along the direction of the air stream. an air passage 70,provided with a calibrated restrictor or orifice 71, a chamber 72 and apassage 73 which connects the chamber 72 to the pipe 1 downstream of thebutterfly valve 2. The chamber 72 is supplied with emulsified fuelthrough a passage 74 from a well 75 whose lower portion is connected.through a passage 76 with a calibrating orifice 77, to a float chamber78. A float 79 regulates the introduction of fuel into the chamber andmaintains a constant liquid level in the chamber 78. A tube 80 dips inthe well 75 and is formed with orifices 81 situated below the level N.Tube 80 is supplied with air from the air intake 69 through calibratedorifices 82 and 83 located in series relation.

To control the flow-rate in the passage 73., there is inserted into thechamber 72 a casing 84 provided with connectors 85 and 86 for thecooling fluid of the engine to flow in the chamber. The casing 84locates an element 87 responsive to the temperature of the fluid;element 87 may have a closed container locating a body of a materialwhich undergoes a variation in volume as a function of temperature.thereby moving a stem 88. The element 87 is held in position by a nut89. The connection between element 87 and casing 84 is rendered fluidtight by a sealing gasket 90. A spring 91, supported on the end wall ofthe casing, exerts on a washer 92 a resilient force which opposesforward movement of the stem 88. A frusto-conical valve member 93,slidably mounted on the stem 88, is biased into abutting engagement withthe washer 92 by a spring 94. The valve 93 is adapted for sealingengagement with a seat 95 located between an inlet orifice 96 and anoutlet orifice 97 which communicate respectively with the chamber 72 andwith the passage 73. O-ring 98 sealingly separates the casing 84 and thecarburettor and prevents direct flow between the chamber 72 and thepassage 73. A cover plate 99 closes casing 84.

The valve 3 is controlled by an element sensitive to temperature whichis heated by an electrical resistor 100 when an electrical current flowsin the latter responsive to closure of a switch or contactor 101. Thatcontactor may be coupled with the ignition contact of the engine. forsimultaneous closure. The element may be a bimetallic spiral strip 102one end 103 of which is stationary and the other end 104 of which isconnected to an axle 105. Axle 105 carries a lever 106 to which the linkrod 4 is connected.

The valve 3 is also actuatable through conventional means by a pneumaticdevice (not shown), which is sensitive to the pressure prevailing in theintake pipe 1 downstream of the butterfly valve 2.

The device operates as follows:

When the engine is started at low temperature (FIG. 1). the choke valve3 is in its minimum opening position. The contactor 101 is closed andthe resistor 100 heats the bi-metallic element 102 which unwinds andprogressively opens the valve 3 through levers and 6 and link rod 4. Asit opens, the valve 3 reduces the underpressure which prevails at themouth of the main fuel jetting device 67 and there is thus obtained afast reduction in the richness of the ca'rburetted mixture in the maincircuit since the heating up of the bi-metallic element 102 can be fast,within a time period whose length depends on the outside temperature.Since the cooling fluid of the engine remains cold for some time afterstarting. the temperature of element 87 is low and the stem 88 is in theposition of FIG. 1 and retains the valve 93 out of engagement with seat95. Air therefore flows through the passages 70 and 73 and theunderpressure. created in the chamber 72 by the calibrated orifice 71,causes a fuel-air emulsion to flow through the passage 74. There is thusobtained the additional air/fuel mixture which is necessary for correctoperation of the engine as long as it has not reached its normaloperating temperature.

When the element 87 has heated up. the projecting length of the stem 88increases and the available crosssection between the valve 93 and itsseat 95 diminishes.

By selecting the calibrated orifices 77, 83 and 71 appropriately, therichness of the air/fuel mixture delivered to pipe 1 through the passage73 may be made to decrease in proportion to the flow-rate of air inpassage 73. that is on the heating up of the element 87. This heating.which depends on the rise in temperature of the cooling fluid flowing inthe casing 84 through the connectors and 86, is generally fairly slow.Due to the invention, it is hence possible to obtain, during coldoperation of the engine. an enrichment of the carburetted mixture whichis important for starting and initial operation. which then decreasesrapidly by a predetermined amount soon after starting, then whichdecreases slowly by an additonal amount until the normal operatingtemperature of the engine is reached.

When the engine is hot (FIG. 2). the stem 88 overcomes the force ofspring 91 and moves the washer 92 forward and the spring 94 holds thevalve 93 on it seat 95. The stem 88 can continue to elongate by slidingthrough the valve 93 without being subjected to excessive stresses.There is thus obtained an automatic starting and cold operation device,which enables great flexibility in adjustment of the carburettedmixture.

What I claim is:

l. Carburettor for an internal combustion engine.

comprising: an intake pipe; an operator actuatable main throttle memberin said pipe; a main fuel jetting system which opens into said pipeupstream of said th'rottle member for providing fuel to the engineduring operation thereof under load; and an auxiliary cold startingdevice responsive to the temperature of the engine to increase at leastthe flow rate of fuel delivered to the intake pipe, said auxiliarydevice including a passage which opens into said intake pipe downstreamof the main fuel jetting system, a closure valve in said passage. meansfor delivering an air fuel mixture of predetermined richness to saidpassage upstream of said closure valve, first temperature responsivemeans for closing said closure valve when heated to a firstpredetermined temperature. a starting choke valve located in said intakepipe upstream of the main jetting system. and second temperatureresponsive valve actuating means for moving said starting choke valvefrom a min imum opening to a more broadly open position when heated to asecond predetermined temperature. wherein said temperature responsivemeans are constructed and arranged for the choke valve to be moved fromits minimum opening position before the closure valve is closedfollowing starting of the engine.

2. Carburettor according to claim 1. wherein the starting choke valveactuating means are arranged for immediate heating thereof followingstarting of the engine while the means for actuating said closure valveare constructed and arranged to be heated at the same rate as theengine.

3. Carburettor according to claim 1, having an electrical resistorthermally associated with said choke valve actuating means and means forsupplying electrical current to said electrical resistor upon startingof the engine.

4. Carburettor according to claim 3, wherein said second temperatureresponsive means are exposed to a fluid the temperature of which ismodified by operation of the engine.

1. Carburettor for an internal combustion engine, comprising: an intakepipe; an operator actuatable main throttle member in said pipe; a mainfuel jetting system which opens into said pipe upstream of said throttlemember for providing fuel to the engine during operation thereof underload; and an auxiliary cold starting device responsive to thetemperature of the engine to increase at least the flow rate of fueldelivered to the intake pipe, said auxiliary device including a passagewhich opens into said intake pipe downstream of the main fuel jettingsystem, a closure valve in said passage, means for delivering an airfuel mixture of predetermined richness to said passage upstream of saidclosure valve, first temperature responsive means for closing saidclosure valve when heated to a first predetermined temperature, astarting choke valve located in said intake pipe upstream of the mainjetting system, and second temperature responsive valve actuating meansfor moving said starting choke valve from a minimum opening to a morebroadly open position when heated to a second predetermined temperature,wherein said temperature responsive means are constructed and arrangedfor the choke valve to be moved from its minimum opening position beforethe closure valve is closed following starting of the engine. 2.Carburettor according to claim 1, wherein the starting choke valveactuating means are arranged for immediate heating thereof followingstarting of the engine while the means for actuating said closure valveare constructed and arranged to be heated at the same rate as theengine.
 3. Carburettor according to claim 1, having an electricalresistor thermally associated with said choke valve actuating means andmeans for supplying electrical current to said electrical resistor uponstarting of the engine.
 4. Carburettor according to claim 3, whereinsaid second temperature responsive means are exposed to a fluid thetemperature of which is modified by operation of the engine.